The present invention relates generally to a filter bag assembly of the type used in a filter housing designed to remove dust, dirt and other particulate matter from air or other gaseous medium and, specifically, to an improved tensioning mechanism and method for maintaining the filter bags in tension within the filter housing.
Fabric filtration is one technique which has proved to be efficient in separating undesirable particulate matter from a gas stream in industrial environments. Such filtration is typically performed in a dust collection apparatus known in the art as a "bag house." The bag house can be described simply as a sheet metal housing divided into two chambers by a tube sheet. Cylindrical fabric filters are disposed within openings in the tube sheet. Particulate containing gas is blown into one chamber where dust accumulates on the fabric filter as the gas passes through the fabric into the other chamber and out an exhaust. The typical bag house arrangement has a plurality of cylindrical filter bags with closed upper ends which are vertically suspended in the clean air chamber from a bag support framework. The lower ends of the bags are fixed to openings in the tube sheet. Filtration of the gas occurs from inside to the outside of the bags.
When it becomes necessary to clean the filter cake from the fabric bags, the flow of process gas is temporarily interrupted so that reverse air can be forced from the clean air chamber to the dirty air chamber. The reverse flow of cleaning air causes the dust cake on the filter bags to be dislodged and fall through the interior of the bags to the dirty air chamber for removal. In some bag house installations, reverse air cleaning is enhanced by mechanically shaking the fabric filters.
Proper tensioning of the bags plays an important role in limiting fabric collapse during the cleaning process. If the bags are stretched too tightly between the supporting framework and the tube sheet, the bags do not collapse during cleaning but suffer accelerated wear. If the bags are installed too loosely, then the fabric collapses during cleaning and will not permit the dust cake to fall through the bag to the bottom of the dirt chamber.
The installation and maintenance of filter bags of the type used in bag houses has tradionally been a time consuming and costly operation. Prior bag designs have, in general, been difficult to service for purposes of rejuvenation, replacement and installation. A need exists for an improved filter bag assembly and mounting technique which would alleviate the various installation and maintenance problems which have been encountered in the past.